As you say, this is an animal that:
1. did not sweat
2. had non-glandular, almost impermeable skin
3. had an extremely low surface to volume ratio
4. presumably excreted uric acid, rather than urea
The only significant water loss would be through respiration. We've talked
about the disadvantages of the large dead space created by the sauropod neck.
However, it does give the critter an opportunity to minimize fluid loss. (I
don't have any particular mechanism in mind, just physiological opportunity).
Even assuming a fully homeothermic beast, the metabolic rate and respiration
are usually inversely related to body mass. How much water could it possibly
need?
Probably this not an answerable question, but we can't assume the answer is >0
and base skeletal reconstructions on that assumption.
--Toby White
On Friday, October 08, 1999 3:16 PM, Jonathan R. Wagner
[SMTP:znc14@TTACS.TTU.EDU] wrote:
> At 04:55 PM 10/8/99 +0100, Jarno Peschier wrote:
>
> >So how then did Camarasaurus get the water that it would certainly have
> >needed?
> >Or is my "would certainly have needed" is error, with dinosaurs having a
> >non-permeable skin (???), eating vegetable matter with enough water content
> >to
> >sustain them (???) and expending so little water via waste disposal?
> Hmm... all animals need water. Some desert-dwelling animals get all
> the water they need from metabolic water, and don't need any outside water.
> However, to my knowledge, these are very SMALL animals. Here's a good
> question for your local botanist: how much water would plant matter
> available to a high-browser actually contain? I had always assumed that the
> most watery fronds were down low, and if _Camarasaurus_ ate those, the point
> is moot. If there isn't much water in higher leaves and twigs, then the
> theory doesn't hold much... um... doesn't help.
> True, the excretion of uric acid (instead of urea) in reptiles is
> believed to be an adaptation for water conservation. It is parsimonious to
> presume that sauropods excreted this substance. However, it was my
> understanding that, water-proof or not, all terrestrial animals lose water
> through respiration, evaporation from moist exposed tissues (eyes, mouth,
> bodily orofices, etc.). This would explain why I've seen members of so many
> different reptile clades drinking water. So I feel confident in concluding
> that _Camarasaurus_ probably did drink water.
> How did it drink? I dunno, maybe some weird pterosaur would scoop up
> water in its gular sack and dump it down the camy's throat in exchange for
> being allowed to lay its eggs in folds of skin along the sauropod's back.
> Ok, you can laugh, but I ain't the one suggesting they didn't drink water. ;)
>
> At 09:18 AM 10/8/99 -0700, Dan Bensen wrote:
> >I wondered about that too, when I read the Discovery article. Did
> >Camarasaurus
> >live in a dry, desert-like environment? Did its ancestors? Maybe, the
> I believe the Morrisson Formation is hypothesized to have been laid
> down under arid conditions. However, since it is largely a fluvial deposit,
> and since I have heard of many sauropod skeletons being recovered from flood
> or channel deposits, I doubt _Camarasaurus_ was hurting for access to water.
> It's ancestors, well, that's a different issue.
>
> >water-saving adaptations nessisary for living in a desert would have allowed
> >Camarasaurus to develope a neck that reached higher than it could otherwise.
> What would it be eating in the desert that was so high in the air?
> For that matter, I believe _Camarasaurus_ has, proportionately, the shortest
> neck of any Morrisson sauropod. Still, it is an interesting hypothesis. :)
>
> Wagner
>
>
------------------------------------------------------------------------------
> --
> Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
> "Why do I sense we've picked up another pathetic lifeform?" - Obi-Wan Ke
nobi